This invention relates to photography and, more particularly, to additive color screens and processes for preparing same.
In general, color screen elements comprise a screen pattern formed of a plurality of light-transmitting colored elements which are each of an independent primary color and which are generally classifiable into different groups in accordance with the color of said elements. Thus, a conventional three-color additive screen generally has a set or group of red-colored filter elements, a set of blue-colored filter elements, and a set of green-colored filter elements. These filter elements are ordinarily in a mosaic or geometrical pattern in a random or predetermined distribution.
Color screen elements may be prepared by a variety of mechanical or photomechanical methods. A particularly suitable method of preparing color screen elements is disclosed and claimed in U.S. Pat. No. 3,284,208, issued Nov. 8, 1966 to Edwin H. Land. The aforementioned patent is directed to a process which comprises successively coating the smooth surface of a lenticular film with a plurality of photosensitive layers and sequentially subjecting the coatings to selectively displaced radiation incident on and focused by the indicated lenticules. Subsequent to each exposure, unexposed coating is removed and the remaining exposed area dyed with the appropriate dyes to provide the desired series of chromatic filter elements. U.S. Pat. No. 3,284,208 is incorporated herein by reference in its entirety.
However, a number of problems are involved in the selection of the dyes for use in the above-mentioned processes. The primary consideration in the selection of the dye is, of course, the color produced thereby.
Stability to light is of prime importance to insure that the color will remain true substantially indefinitely since the color screen will be in position prior to use on the film and, of course, subsequent to exposure and processing of the film and subjected to light from projection lamps of high intensity for view. The compatibility and dyeability of the dye with respect to the dyeable substrate must also be considered as well as the fastness or retention of the dye in a given substrate since the migration of the dye from one area into an adjacent area dyed with a different color dye would result in the lack of sufficient color accuracy and intensity with respect to the area dyed, accuracy of boundaries between dyed areas, by such a redyeing or mixing of the colors of adjacent areas.
The dye must also possess the property of resistance to photographic processing compositions, for example, alkaline processing compositions such as those set forth in U.S. Pat. No. 2,614,926. While the susceptibility to degradation by contact with processing compositions can be minimized to some degree by the employment of barrier coats of suitable polymeric materials, for example, between each adjacent colored filter element or over all of the filter elements, such additional layers are not entirely desirable because of the possible loss of resolution in the resulting photographic image.
In summary, the dye system employed should readily dye the substrate but be firmly retained and anchored to the substrate to avoid migration and water fast to avoid dye migration under conditions of high humidity.